1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and a method for transferring a substrate during processing. More particularly, embodiments of the present invention provide apparatus and method for supporting a substrate during loading and unloading.
2. Description of the Related Art
Sub-micron multi-level metallization is one of the key technologies for the next generation of ultra large-scale integration (ULSI). The multilevel interconnects that lie at the heart of this technology require planarization of interconnect features formed in high aspect ratio apertures, including contacts, vias, trenches and other features.
Planarization is generally performed using Chemical Mechanical Polishing (CMP) and/or Electro-Chemical Mechanical Deposition (ECMP). A planarization method typically requires that a substrate be mounted in a carrier head, with the surface to be polished exposed. The substrate supported by the carrier head is then placed against a rotating polishing pad. The carrier head holding the substrate may also rotate, to provide additional motion between the substrate and the polishing pad surface. A polishing solution is usually supplied to the rotating polishing surface to assist the planarization process.
During the planarization process, the substrate is generally secured on the carrier head from the backside of the substrate, for example by forming vacuum cups between a membrane on the carrier head and the backside of the substrate. Prior to or after the planarization process, a load cup is generally used for substrate transferring to and from a carrier head.
In the state of the art load cup may have a substrate supporting means, for example, support fingers, configured to hold a substrate and transfer the substrate to and from the carrier head. When unloading a substrate from a carrier head, the membrane is usually inflated to release the vacuum cups between the membrane and the backside of the substrate. The substrate will then fall off the carrier head to a load cup underneath under the effect of gravity. FIG. 1 schematically illustrates a substrate holder used in the state of the art load cup. A carrier head 10 having a membrane 11 configured to secure a substrate 12 thereon. The membrane 11 is inflated so that the substrate 12 is no longer drawn to the carrier head 10 by suction. A substrate holder 15 having a plurality of support fingers 14 is positioned underneath the carrier head 10 to catch the substrate 12 once the substrate 12 falls off the carrier head 10 under the effect of gravity. During this transferring process, a processed surface 13 of the substrate 12 is exposed to air or other process environment. The processed surface 13 is generally wet from polishing solutions on polishing stations. Structures, such as copper structures, easily corroded when exposing to air in a wet condition.
The state of the art load cup has several limitations. First, the time requires to load/unload a substrate from a carrier head is relatively long and unpredictable since the load cup passively waits for gravity to take effect. Second, a substrate to be loaded/unloaded is generally wet and exposed to atmosphere during unloading resulting in corrosion on the processed surface.
Therefore, there is a need for apparatus and method to transfer a substrate at an increased and predictable rate and with decreased corrosion.